The invention relates to a process and a system for determining fuel consumption of a motor vehicle.
As a result of growing awareness of the environment and of increasing fuel prices, low fuel consumption is becoming more and more important to the users of motor vehicles. Systems for determining the fuel consumption in motor vehicles are therefore used to an increasing degree.
It is an object of the invention to create a process and a system for determining fuel consumption of a motor vehicle by which a reliable signaling of the fuel consumption will be permitted.
This and other objects are achieved according to a first and second aspect of the invention, by a process and system for determining fuel consumption of a motor vehicle. A first mean fuel consumption, which cannot be reset under a user's influence, is determined. A second mean fuel consumption, which can be reset under a user's influence, is determined as a function of several measured values. A third mean fuel consumption is determined. At the beginning of a predefined time period, which starts with a resetting of the second mean fuel consumption influenced by the user, this third mean fuel consumption is set to be equal to the first mean fuel consumption; between the beginning and the end of the predefined time period, it is set to be a weighted mean of the first mean fuel consumption and the second mean fuel consumption; and, starting at an end of the predefined time period, it is set to be equal to the second mean fuel consumption. A signal is generated for signaling the third mean fuel consumption.
The above process and corresponding system have the advantage that, also immediately after a resetting of the second mean fuel consumption, a determination of the third mean fuel consumption and a generating of the signal for signaling the third mean fuel consumption become possible, with particularly low fluctuations of the values of the signal. While the determined third mean fuel consumption at the beginning of the predefined time period is determined by the first mean fuel consumption, at the end of the predetermined time period, it will more and more approach the second mean fuel consumption.
In an advantageous further development, the third mean fuel consumption is determined as the sum of the product of the second mean fuel consumption and of a weighting factor and the product of the first mean fuel consumption and the difference of one and the weighting factor. At the beginning of the predefined time period, the weighting factor is set to a zero value. Within the predefined time period, the weighting factor is determined in a linearly increasing manner as a function of a time period expired since the resetting of the second mean fuel consumption. As of the end of the predefined time period, the weighting factor is set to the value of one. This has the advantage that a simple linear development of the time sequence of the weighting factor becomes possible from the zero value at the beginning of the predefined time period to the value of one as of the end of the predefined time period.
In a further advantageous development, it is checked whether the motor vehicle is stopped and, while the motor vehicle is recognized to be stopped, the time period is kept constant that has expired since the resetting of the second mean fuel consumption. This has the advantage that the time period that has expired since the resetting of the second mean fuel consumption remains unchanged when the vehicle is stopped and can continue to run again when the vehicle is restarted. The predefined time period for the signaling of the third mean fuel consumption can thereby be utilized in a maximal fashion.
In a further advantageous development, the motor vehicle is recognized to be stopped when the speed of the motor vehicle falls below a predefined speed threshold value. This has the advantage that, particularly at low vehicle speeds, the time period since the resetting of the second mean fuel consumption remains unchanged, and thereby an influence of values of the second mean fuel consumption that fluctuate particularly severely at low vehicle speeds can be avoided. The predefined time period for the signaling of the third mean fuel consumption can therefore be maximally utilized.
In a further advantageous development, the predefined threshold value of the speed is approximately equal to 15 km/h. As a result, a starting or a stopping of the vehicle, as well as stop-and-go traffic, can be taken into account during the stopping of the time period expired since the resetting of the second mean fuel consumption.
In a further advantageous development, an actual fuel consumption is determined as a function of several measured values. It is checked whether the actual fuel consumption is greater than the third mean fuel consumption and, while this is the case, the time period is kept constant that has expired since the resetting of the second mean fuel consumption. This has the advantage that the time period since the resetting of the second mean fuel consumption remains unchanged when the third mean fuel consumption falls below the determined actual fuel consumption, and thus a faulty calculation of the third mean fuel consumption can be avoided. Furthermore, the time period for the adaptation of the signaling of the third mean fuel consumption can be utilized as well as possible.
According to a third aspect, the invention is characterized by a system which includes a device for determining the fuel consumption of the motor vehicle and a signaling unit. The signaling unit is constructed for receiving the signal for signaling the third mean fuel consumption and for signaling.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.